I bought the brown in small and it fits & looks great. I'm 5'7" with an athletic build and a 30" waist and a 40" chest. If you've got a belly it'll be an uncomfortable fit I'm guessing as it is snug.
This jacket is perfect. I’m 5’11” 185 lbs and I bought the Black jacket in a Medium and the size fits excellent. The order was shipped quickly and I would highly recommend. 10/10